MFC r312559:

MFC r312559:

Fix misc Coverity defects in camdd(8)

CID 1341620	Fix a small memory leak
CID 1341630	Though this is technically a false positive, rearrange the
		code for clarity.
CID 1341635	Eliminate dead code
CID 1368663	Fix a double mutex unlock in the error path

Also:
* Use sig_atomic_t for variables accessed from signal handlers
* Don't conditionalize free(3) on its argument being non-null

Reported by:	Coverity
CID:		1341620 1341630 1341635 1368663
Reviewed by:	ken
MFC after:	4 weeks
Sponsored by:	Spectra Logic Corp
Differential Revision:	https://reviews.freebsd.org/D9237

git-svn-id: svn://svn.freebsd.org/base/stable/10@314438 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f